Bonding together surfaces of two bodies with a joining or bonding material often includes the application of heat from an external heat source. During the bonding process, the external heat source typically heats not only the bonding material, but the bodies which are to be joined as well. Unfortunately, if the bodies are heat sensitive, they may be damaged from such heating. Also, if the bodies and bonding material have differing thermal characteristics, as is often the case, the bodies and bonding material may cool at different rates and create trapped mechanical stresses that may eventually cause failure of the resulting bond.
For example, semiconductor devices, such as semiconductor die, are often bonded to a substrate or carrier, such as a copper leadframe, for example, using an electrically conductive bonding material, such as a lead/tin solder. According to conventional bonding techniques, an external heat source, such as an oven, for example, heats the leadframe to a desired temperature (e.g. 400-degrees C.) and solder is applied to the leadframe at a location where the semiconductor die is desired to be attached. The semiconductor die is then placed on the solder and the entire assembly is heated to melt the solder and bond the semiconductor die to the leadframe. The assembly is then removed from the oven and cooled.
While such an approach effectively bonds the semiconductor die to the leadframe, the semiconductor die may potentially be damaged if too high a temperature is employed. Additionally, due to differing coefficients of thermal expansion between the semiconductor die and the leadframe, the semiconductor die and copper leadframe contract or shrink at different rates resulting in the creation of trapped stresses within the silicon of the semiconductor die, which can lead to failure of the bond and/or semiconductor die.
For these and other reasons there is a need for the embodiments according to the present disclosure.